Bob, just to point out, nitrogen is not the only organic by-product in the system. I'm not even sure a skimmer would/could remove nitrogen. A DSB and/or rock is best at removing that. The skimmer is used to remove other compounds....I can dig up some names for these if you like.SOme of these can/will build up over time if you don't have a skimmer or do water changes
You are correct in saying a skimmer may not be required and if that works for you, you sacved some money!!
However; when I tell new reefers to not listen to you and invest in a skimmer, I do this because I believe it to increase their chances of being successful, not because you're way won't work. You show that it does work for you. You have also been doing this along time. After the new reefer has done this as long, I also would encourage experimenting with different techniques.
I'm not trying to be a know it all, or say you are wrong. I'm just giving advice that I think will increase the likelihood of success for the new guy!